// 清除默认样式
* {
    margin: 0;
    padding: 0;
  }
  
  html, body, #app {
    width: 100%;
    height: 100%;
    overflow: hidden;
  }
  
  ul, ol, li {
    list-style: none;
  }
  
  input, select, button, textarea {
    outline: none;
  }
  
  a, a:hover, a:active, a:link, a:visited {
    text-decoration: none;
  }
  